1. Field of the Invention
This invention relates to a hydraulic or pneumatic actuation system for switching hydraulic/pneumatic power to different hydraulically/pneumatic driven components of automatic swimming pool cover systems in a timed, sequenced, and velocity controlled manner. The invented system is particularly appropriate for passively responding buoyant slat pool cover systems.
2. Description of the Prior Art
Automatic pool cover systems utilizing interconnected rigid buoyant slats which roll up on a submerged or elevated drum popular in Europe are described by U.S. Pat. No. 3,613,126, R. Granderath. These pool cover systems utilize passive forces arising from buoyancy or gravity for propelling or extending the cover across a pool. With either buoyancy or gravity, there must be some mechanism to prevent a retracted cover from unwinding responsive to the passive force. Such passive force systems also have a disadvantage in that the passive force must be overcome during retraction. Granderath teaches a worm gear drive mechanism for winding the cover and preventing cover drum rotation when not powered. The slats for such pool cover systems are further described in U.S. Pat. No. 4,577,352, Gautheron.
U.S. Pat. No. 4,411,031 Stolar describes a system similar to Granderath where instead of rigid hinged buoyant slats, various floating sheet materials such as a polyethylene polybubble, or a laminate of vinyl sheeting and foamed substrate, are floated on the surface of the water. Similar to Granderath extension the cover across the pool is reliant on buoyant and gravitational forces.
Pool covers which employ floating slats or like materials, that depend on buoyancy to propel the cover across the pool, most typically wind the cover onto a roller drum which is positioned below the water surface. When the cover is fully retracted from the swimming pool surface and fully wound onto the cover drum, the upper extremity or front/leading edge of the cover and drum typically are at least two inches below the water surface of the pool. In some cases, the cover and drum are located in a separate water filled niche next to the pool. In other instances the cover and drum may be located near the bottom of the pool, or in a special hidden compartment underneath the pool floor to aesthetically hide the cover and roller drum, and so that the mechanism does not interfere with swimmers.
Many known European buoyant pool cover systems include a hinged lid covering an under water cover drum assembly enclosure. Typically, the hinged lid is shortened so as to leave a gap or aperture sufficient through which the slatted cover to pass on extension and retraction. The front/leading edge portion of the cover is not fully retracted beneath the lid and left, so as to lead the cover properly through the aperture upon allowing the cover to unwind from around the cover drum on extension passively driven by buoyancy. This is important because if the cover does not feed properly through the aperture, and becomes obstructed or jams, the cover would continue to unwind “crumpling” and expanding diametrically and underneath the lid causing severe damage to the cover slats.
Also Health and Safety inspectors in many jurisdictions in the United States and elsewhere as well as insurance companies, do not allow or will not insure swimming pools which have underwater apertures that can entrap a swimmer. In short, for safety reasons, underwater pool cover assembly trenches/wall recesses must be completely enclosed, requiring a lid assembly completely covering the trench/recess and some mechanism for opening the lid to allow cover deployment and then closing the lid after cover retraction.
Another problem with slatted and other buoyant pool cover systems that emerge from an underwater trench in a pool floor or an underwater recess in sidewall of a pool, is that the cover initially moves vertically due to buoyancy, and upon breaking the water surface, changes direction due to gravity to float horizontally across the pool surface. Typically, measures are be taken to somehow mechanically force the front/leading edge of a buoyant cover to assume a proper orientation and direction upon emerging vertical out the pool surface so that it flops in the proper horizontal direction. For example, often the leading slat component section is pre-bent or fixed in an orientation towards the desired direction of horizontal travel. Pre-bending doesn't work when the front/leading edge is a foot or more below the water surface. In such instance the ‘pre-bending’ and the cover will often “snake” back and forth below the water making direction of travel relative to the vertical upon breaking water surface unpredictable. A solution is to slow the travel to the buoyant cover in the unwinding direction sufficiently to off set the acceleration forces due to buoyancy effectively controlling extension, until the front/leading edge of the cover breaks water surface.
German patent DE 3032277 A1 R. Granderath. a pool floor cover system lid covering system is described that includes an air bladder induction system for opening a lid of a cover drum assembly enclosure prior to allowing the cover to unwind to close when the cover is fully retracted. German patent DE 198 07576 A1, K. Frey describes a floating door that is mechanically moved vertically from covering an underwater pool cover trench in the floor of the pool to the water suface by means of a cables wound up on reels. K Frey also describes a worm gear reducer drive similar to that used to drive the pool cover drum driving the door closing system,
The common practice (presented in trade show exhibits and actual installations) is to actuate a hinged lid system covering an underwater pool cover trench or wall recess with a separate worm gear reducer drive powered by an electric motor and connected to the hinged lid shaft. Electric-mechanical limit switches devices are typically used to stop lid opening at the suitable point that allows the buoyant cover to unwind from around the cover drum with out interference due to the lid. To explain, depending on the thickness of the particular buoyant cover, hinged lids normally only have to rotate 40 to 60 degrees from the horizontal in the case of a pool cover trench and 30 to 50 degrees from the vertical in the case of a side wall recess to create a sufficient aperture for a buoyant cover to pass through on its way to the water surface.
Separate gear drive systems for pool cover enclosure lids with associated limit switches governing travel for such a limited distances are costly. Further, timing of the drive systems must be coordinated with those restraining/driving cover drum rotation on cover extension/retraction. Furthermore, electric drives necessitate the supply of electrical current proximate the swimming pool, creating a shock safety hazard. Moreover electrical components in a moist pool environment are subject to galvanic corrosion rendering them unreliable over time.